PROBLEM TO BE SOLVED: To realize and to maintain high coupling efficiency by highly accurate alignment in an optical system which aligns an incident light beam with an end of an optical fiber while avoiding reduction in image quality due to multiple light reflection of a lens.SOLUTION: An optical coherent tomographic apparatus comprises: an incident-side waveguide part 500 for making a light beam incident to an optical system； an incident-side strong power lens 502 for collimating the incident light beam； an emission-side waveguide part end 532 for emitting a light beam from the optical system； an emission-side strong power lens 530 for collecting collimated light beams to the emission-side waveguide part end 532； and a weak power lens 531 movable in at least one direction on a plane perpendicular to the optical axis between the emission-side waveguide part end 532 and the emission-side strong power lens 530. When the coupling efficiency of the optical system is equal to or greater than a predetermined value, the weak power lens 532 is arranged such that the region around the optical axis of the weak power lens does not overlap the regions around the optical axes of the emission-side waveguide part end 532 and the emission-side strong power lens 530.SELECTED DRAWING: Figure 2【課題】 入射された光束を光ファイバ端へ位置合わせする光学系において、レンズの多重反射光による画質低下を回避しつつ、高精度なアライメントによる高結合効率化とその維持を実現する。【解決手段】 光学系に光束を入射する入射側導波部５００と、入射した光束を平行化するための入射側強パワレンズ５０２と、光学系から光束を出射する出射側導波部端５３２と、出射側導波部端５３２へ平行光を集光するための出射側強パワレンズ５３０と、出射側導波部端５３２と出射側強パワレンズ５３０の間に光軸に垂直な平面内の少なくとも１方向に移動可能な弱パワレンズ５３１を有し、光学系の結合効率が所定値以上であるとき、出射側導波部端５３２と出射側強パワレンズ５３０の光軸中心近傍領域に対し、弱パワレンズ５３２の光軸中心近傍領域が重ならない配置とする。【選択図】 図２
